The main purpose of this study will be to evaluate, both in vitro and in vivo, the function and structure of vascular cells obtained from normal and atherosclerotic blood vessels. Particular emphasis will be placed on the comparison of characteristics of human endothelial and smooth muscle cells from fetal and adult arteries and veins in vitro and their interaction with circulating lipoproteins and platelets. The effects on cell growth and behavior of lipoproteins isolated from selected donors undergoing cardiac catheterization with or without cineangiographic evidence of coronary artery disease will be specifically studied and compared with synthetic glycolipids incorporated into reconstituted natural lipoproteins. A new method, developed in this laboratory to induce reproducible and rapidly resolving multiple arterial injuries, will be applied to the evaluation of vascular repair with or without the presence of acute dietary hypercholesterolemia or during different stages of progression and regression of experimental atherosclerosis. Similarly, the role of thrombocytopenia, thrombocytosis and platelet release reactions will be compared with the pharmacological effects of drugs known to alter platelet function on arterial reparative processes.